1. Field of the Invention
The present invention relates to a pressure relief device and, more particularly, to a co-axial pressure relief device for an air inflator.
2. Description of the Related Art
A conventional pressure relief device for an air inflator in accordance with the prior art shown in FIGS. 6 and 7 is disclosed in the U.S. Pat. No. 4,998,562 and comprises a guide pipe 13 having a first end connected to an air cell 14 and a second end connected to an inflatable body (not shown), a pressure relief tube 12 mounted on and perpendicular with the guide pipe 13, and a rotation screw 11 rotatably mounted on the pressure relief tube 12. The air cell 14 has an air inlet hole 17. Thus, when the rotation screw 11 is tightened, the air contained in the air cell 14 is compressed to pass through the pressure relief tube 12 into the inflatable body to inflate the inflatable body, and when the rotation screw 11 is loosened, the air contained in the inflatable body is released outwardly through a gap between the rotation screw 11 and the pressure relief tube 12 to release the pressure in the inflatable body.
However, the conventional pressure relief device has a double-axis type pressure relief structure, so that the conventional pressure relief device has a complicated construction, thereby increasing the costs of fabrication. In addition, the air inlet hole 17 is located at a rear portion of the air cell 14, so that when the air cell 14 is compressed by a user, the air inlet hole 17 is held by the user's one hand, thereby easily causing an uncomfortable sensation to the user during operation of the air cell 14. Further, the rotation screw 11 and the pressure relief tube 12 are protruded outwardly from the guide pipe 13 in a perpendicular manner, so that the rotation screw 11 and the pressure relief tube 12 are easily deformed or broken due to hit of an external force. Further, the rotation screw 11 and the pressure relief tube 12 are protruded outwardly from the guide pipe 13, so that the pressure relief device has a larger volume, thereby causing inconvenience in packaging, storage and transportation of the pressure relief device.
Another conventional pressure relief device for an air inflator in accordance with the prior art shown in FIG. 8 comprises a guide pipe 16 having a first end connected to an air cell 14 and a second end connected to an inflatable body (not shown), a pressure relief bar 18 mounted on and perpendicular with the guide pipe 16, and a push button 15 movably mounted on the pressure relief bar 18. The air cell 14 has an air inlet hole 17. Thus, when the push button 15 is pressed, the air contained in the inflatable body is released outwardly through a gap between the guide pipe 16 and the pressure relief bar 18 to release the pressure in the inflatable body.
However, the conventional pressure relief device has a double-axis type pressure relief structure, so that the conventional pressure relief device has a complicated construction, thereby increasing the costs of fabrication. In addition, the air inlet hole 17 is located at a rear portion of the air cell 14, so that when the air cell 14 is compressed by a user, the air inlet hole 17 is held by the user's one hand, thereby easily causing an uncomfortable sensation to the user during operation of the air cell 14. Further, the push button 15 and the pressure relief bar 18 are protruded outwardly from the guide pipe 16 in a perpendicular manner, so that the push button 15 and the pressure relief bar 18 are easily deformed or broken due to hit of an external force. Further, the push button 15 and the pressure relief bar 18 are protruded outwardly from the guide pipe 16, so that the pressure relief device has a larger volume, thereby causing inconvenience in packaging, storage and transportation of the pressure relief device.